The snap fasteners consisting mainly of a male member and a female member that have been proposed so far include one that has caps combined with a socket/stud having a caulking leg provided at the center of each cap. To attach a snap fastener to pieces of fabric, each caulking leg is pressed through each piece of fabric and its end is inserted through the insertion hole bored in the center of the socket or stud to hold the fabric between the cap and the socket/stud and then fix them by punching for caulking the end of each caulking leg (see, for instance, patent documents 1 and 2). The snap fasteners consisting mainly of a male member and a female member that have been proposed so far also include taped fasteners made of synthetic resin produced by molding them on both sides of tape (see, for instance, patent document 3). These snap fasteners are required to have a moderate degree of stiffness and toughness. In particular, the sockets and studs, which are fastened and unfastened repeatedly, must have a proper degree of toughness. In addition, a cap provided with a caulking leg must have a stiffness required to penetrate fabric and a toughness required to deform without suffering from cracking when caulked.
To meet these required characteristics, plastic fasteners made of polyacetal resin have been proposed (see, for instance, patent document 4). However, polyacetal resin softens at a low temperature of about 170° C., causing some problems when, for instance, ironed at a high temperature. The resin may also cause environmental problems because it is likely to release environmental hormones in some processing steps. There have been other investigations proposing taped fasteners that are made of polyamide resin from the viewpoint of heat resistance (see, for instance, patent documents 5 to 6). Although high in heat resistance, polyamide resin is low in stiffness and toughness, leading to molding products that are likely to suffer from stiffness deterioration when absorbing water.